Learning Forum

[thach-hoang.nguyen]

Hello,

I'm trying to simulate the deployment of the stent and i've tried a lot of times but it always failed to find a converged solution for the deployment.

The simulation is like in the image 1. The simulation has 2 steps. The first step i add a radial displacement also i added displacements Y=0 and Z=0 in the cylindrical reference of the stent on the 3 vertices in one end of the stent. So I was able to easily find a converged solution and in this step, the stent is well compressed. Second step, I deactivated the radial movement on the stent and the stent will touch the silicone cylinder (mock artery) but I cannot find the converged solution (image 2). I have already tried several methods or non-linear controls but in any case, it did not work. Can anyone help me resolve this problem please? Thank you so much.

Some of the useful informations you can use:

• Superelastic Nitinol is used for stent
• The mock artery is assumed to be isotropic linear elastic (for now)
• Image 3 is the information about the substep of step 2
• Image 4 is the graph of times/cumulative iteration ( the simulation were always stopped at the beginning of step 2)
• The simulation is in static and the large deflection is on. 
• The simulation worked when the stent is assumed isotropic linear elastic and when the large deflection is off.

Thank you for your help and help a good day/evening.

[thach-hoang.nguyen]

Hello,

Can someone please help me with this matters? 

Thank you and have a nice day

[Ashish Khemka]

Hi Hoang,

Try using a coarse mesh on the sheath. Can you show the snapshot of material properties? Also, another suggestion for simplicity, try using a 60-degree portion of the model (assuming symmetric loading).

 

Regards,

Ashish Khemka

[thach-hoang.nguyen]

Hello Ashish,

Using coarse mesh doesn't work so im trying have more elements at the cylinder to find the converged solution. 

For the material of the cylinder, i'm using isotropic linear elastic with Young modulus of 1,0  MPa and Poisson of 0,3

For the material of the stent, im using superelastic:

• Lineair elastic

+ Young modulus : 50 GPa

+ Poisson: 0,3 

Superelastic:

+ Sigma SAS: 500 MPa

+ Sigma FAS: 600 MPa

+ Sigma SSA: 200 MPa

+ Sigma FSA: 100 MPa

+ Epsilon: 0,04

+ Alpha : 0

+ Es: 19 GPa

For your suggestion, i'm more interested in the stent with the full portion. Do you have any ideal that can fix this problem? Thank you have a good day!!